Low MPG

Discussion in 'Gen 2 Prius Fuel Economy' started by midi_ring, Jun 6, 2026 at 2:12 AM.

  1. midi_ring

    midi_ring Junior Member

    Joined:
    Dec 5, 2024
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    Location:
    usa
    Vehicle:
    2005 Prius
    Model:
    N/A
    yet another mpg thread. I ran Dr. Prius, and says my battery health is at 78%. I don't know exactly how to run other tests I've seen suggested here on this forum.

    But, I have bad mpg. Like, I doordash, so I basically do the same thing all the time. Same hwy miles, same city, rural road driving. When I got the car, it did around 47-48mpg normally. Few months after I got it, the battery got the Red triangle of death. Found one bad cell. Replaced it, refurbished all the other batteries with a hobby charger, to around 5500 ma each. Took 3 weeks plus. (got them to 5000 first then went ahead to see how much further I could push them, about 3 more charges each). I balanced the battery, and put it back in the car.

    I started seeing 50-52mpg consistently. Lasted about 4-5 months, and recently, I had had that coolant problem the entire time, with it hunting. But my MPG started lowering, to around 45mpg-ish. I replaced that coolant thing. Maybe improved for a bit, but, for the past 8 fillups, I believe I have averaged 40-44mpg. Best out of them was one at @48mpg. But evenly besides that either getting 40-44mpg. The car will show me about 46-47mpg, but at the pump thats what I see. I fill up the same every time.

    Before with the 50+mpg, i would fill up the same and go by that to determine my mpg.

    So, can someone explain to me how to run a different test anyone can maybe tell me something about, or any other things I could do? Cars got 105K miles. 2006. One thing told me that i had an unbalanced blade at #6..

    thats it. Any tips?